Background

Mucosal healing (MH) is an important treatment goal, and is usually assessed by endoscopic evaluation in ulcerative colitis. Recent guidelines have noted that there is a good correlation between the paediatric ulcerative colitis activity index (PUCAI) and endoscopic Mayo Score, and a recommendation that the PUCAI can be used as a proxy for MH. However, no previous study has prospectively validated the use of PUCAI as a proxy for MH specifically during clinical remission. The goal of the present study was to evaluate if the PUCAI accurately reflects MH in children with clinical remission.

Methods

Single center prospective observational cohort with blinded assessment of endoscopic Mayo score, involving consecutive pediatric patients ≤18 years old in clinical remission or borderline clinical remission due to occasional symptoms. All children with UC underwent sigmoidoscopy 3–4 months after obtaining remission. PUCAI was calculated and registered prior to endoscopy. Complete clinical remission was defined as PUCAI <10. Borderline clinical remission was defined as involvement of only one symptom category that was inconsistent (i.e. occasional mild bleeding, abdominal pain or liquid stools without blood). Mayo endoscopic score was performed at time of endoscopy by the endoscopist and rectum and sigmoid were photographed. Mayo score was reviewed independently by another experienced gastroenterologist blinded to both the PUCAI and endoscopists assessment. The highest Mayo score of either segment was used as the patient endoscopic Mayo score.

Results

19 patients (47.4% male, 52.6% female) mean age 15.7±2.2 met study inclusion criteria. 79% were asymptomatic with normal PUCAI, the rest had suspected clinical remission with occasional symptoms. There was a good interobserver agreement between the Mayo score that evaluated between the two experts independently (Phi coefficient 0.772, Cramer's V 0.772). Among patients with PUCAI <10, Mayo score 0 were seen in 66.7%, Mayo 2–3 were seen in 33.3%. Among patients in questionable remission, Mayo score 0 were seen in 75%, Mayo 1 were seen in 25%. There was poor agreement between Mayo score and PUCAI, knowing one value did not significantly increase the chances of knowing the other value (Phi coefficient 0.073, Cramer's V 0.073, The Goodman and Kruskal tau coefficient 0.005, all were not significant p=0.75).

Conclusion

The data from this cohort of patients assessed prospectively during clinical remission suggests that a clinically relevant proportion of patients had active endoscopic disease, despite normal PUCAI scores. Caution should be used in extrapolating from PUCAI to MH specifically among patients with clinical remission after therapy.